The invention relates to a shaver comprising a shaving head including at least one cutting blade and two skin-supporting members, the cutting blade having a cutting edge extending perpendicularly to a shaving direction of the shaving head, and the skin-supporting members being arranged, viewed in the shaving direction, respectively, in front of and behind the cutting blade and extending substantially in a contact surface wherein, in operation, the shaving head contacts a skin surface to be treated, while the cutting blade and the skin-supporting members are secured to a sub-frame, which is coupled to a main frame and can be displaced, against a spring force, with respect to the main frame.
The invention also relates to a shaving head which can suitably be used in a shaver in accordance with the invention.
A shaver of the type mentioned in the opening paragraph is disclosed in WO-A-97/26119. The shaving head of the known shaver comprises two mutually parallel cutting blades which, viewed in the shaving direction, are arranged between the two skin-supporting members. If the user places the shaving head on the skin surface, an exerted press-on force is transmitted to the skin surface mainly via the two skin-supporting members. As a result, a contact force exerted by the cutting blades on the skin surface is limited, and lesions to the skin surface, which could occur during moving the shaving head in the shaving direction over the skin surface as a result of too large a contact force between the cutting blades and the skin surface, are precluded as much as possible. In the known shaver, the main frame of the shaving head is attached to a handle, while the sub-frame of the shaving head is attached to the main frame by means of four mechanical torsion springs. As a result, when the shaving head is moved over the skin surface, the sub-frame follows the contours present in the skin surface as accurately as possible, so that the cutting blades continually contact the skin surface as completely as possible.
A drawback of the known shaver resides in that a skin curvature, which is present at the location of the cutting blades and which develops under the influence of the press-on force, depends upon a size of said press-on force. If the press-on force is comparatively small, the skin curvature is comparatively small too, so that only a comparatively limited smoothness of the skin surface is attained. If the press-on force is relatively large, the skin curvature is comparatively large too, which results in a very smooth skin surface, but which may also lead to skin irritations as a result of a comparatively large contact force between the cutting blades and the skin surface. Consequently, a shaving result obtained by means of the known shaver is highly personal and depends, in particular, on the press-on force exerted by the user when he places the shaving head on the skin surface.
It is an object of the invention to provide a shaver of the type mentioned in the opening paragraph, by means of which an achieved shaving result is much less personal, in particular, much less dependent on the press-on force exerted by a user when placing the shaving head on the skin surface.
To achieve this object, a shaver in accordance with the invention is characterized in that the main frame comprises two further skin-supporting members which, viewed in the shaving direction, are arranged, respectively, in front of and behind the sub-frame and which extend substantially in the contact surface. If a user places the shaving head of the shaver in accordance with the invention on the skin surface, an exerted press-on force is transmitted to the skin surface mainly via the two further skin-supporting members of the main frame. As a skin curvature develops between the two further skin-supporting members as a result of the press-on force, the skin surface between the two further skin-supporting members is also supported by the two skin-supporting members of the sub-frame, said sub-frame being moved against the spring force, under the influence of the skin curvature, with respect to the main frame to an equilibrium position wherein the spring force is substantially in balance with a contact force exerted by the skin surface on the sub-frame. As the size of the skin curvature depends upon the size of the press-on force, said equilibrium position also depends upon the size of the press-on force. The shaving head preferably comprises means for exerting the spring force, wherein said spring force depends as little as possible, at customary values of the skin curvature, on the position of the sub-frame with respect to the main frame. As a result, it is achieved that a supporting force, by means of which the skin surface is supported in the equilibrium position by the skin-supporting members of the sub-frame and which is determined by the size of the spring force, depends as little as possible on the skin curvature between the two further skin-supporting members and hence also depends as little as possible on the exerted press-on force. As a skin curvature present between the two skin-supporting members of the sub-frame, i.e. at the location of the cutting blade, is determined by said supporting force of the skin-supporting members of the sub-frame, this skin curvature present at the location of the cutting blade also depends as little as possible on the exerted press-on force, so that also the shaving result achieved depends as little as possible on the exerted press-on force.
A particular embodiment of a shaver in accordance with the invention is characterized in that the spring force is directed towards the contact surface, and, in a state wherein the shaving head does not contact the skin surface, the sub-frame rests against a stop of the main frame under the influence of the spring force. By using said stop, it is achieved in a constructionally simple way that, in said state, the spring force has a predetermined, desired value which is determined by a desired skin curvature between the two skin-supporting members of the sub-frame.
A further embodiment of a shaver in accordance with the invention is characterized in that the sub-frame is secured to the main frame by means of a mechanical spring unit, and is at least tiltable with respect to the main frame about two mutually perpendicular tilt axes and displaceable with respect to the main frame in a displacement direction perpendicular to said tilt axes, thereby deforming the spring unit. As a result, when the shaving head is moved over the skin surface, the sub-frame follows, to a large extent, the contours present in the skin surface, so that the cutting blade stays in full contact, or substantially full contact, with the skin surface, resulting in an effective shaving process.
Yet another embodiment of a shaver in accordance with the invention is characterized in that the spring unit comprises a central portion and two pairs of leaf springs facing away from each other, which leaf springs each extend from the central portion in a direction substantially perpendicular to the shaving direction, and each support the sub-frame at a location close to a corner. As a result, the construction of the spring unit is simple, the central portion and the two pairs of leaf springs being producible as a single part from, for example, a metal sheet. By applying the two pairs of leaf springs, it becomes possible to tilt the sub-frame, with respect to the main frame, about two mutually perpendicular tilt axes, which extend in an imaginary plane which extends approximately parallel to the contact surface, and to displace said sub-frame in a displacement direction approximately perpendicular to the contact surface.
A particular embodiment of a shaver in accordance with the invention is characterized in that the central portion of the spring unit is provided with a sphere segment-shaped supporting element with which the spring unit rests against the main frame. By using the sphere segment-shaped supporting element, the tiltability of the sub-frame, with respect to the main frame, about the two mutually perpendicular tilt axes is improved.
A further embodiment of a shaver in accordance with the invention is characterized in that the shaving head is provided with means for adjusting the spring force. Since the spring force can be adjusted by means of said means, the contact force exerted by the skin surface on the sub-frame as well as a skin curvature present between the skin-supporting members of the sub-frame are adjustable. This enables a user of the shaver to set the spring force at a desired or personally optimum level.
Yet another embodiment of a shaver in accordance with the invention is characterized in that a skin-stretching member is provided on the main frame and/or on the sub-frame, which skin-stretching member is arranged, viewed in the shaving direction, in front of the cutting blade. By using said skin-stretching member, the skin curvature between the two skin-supporting members of the sub-frame and/or between the two further skin-supporting members of the main frame is limited, so that skin irritations and incised wounds, which could occur in the case of too large a skin curvature by contact between the skin surface and the cutting blade, are precluded as much as possible. In addition, the skin-stretching member can also be used as a skin-supporting member, resulting in a reduction of the number of parts of the shaver.
A particular embodiment of a shaver in accordance with the invention is characterized in that a skin-contacting member is provided on the main frame and/or on the sub-frame, which skin-contacting member contains a shaving aid. By using the skin-contacting member, the shaving comfort is increased. The shaving aid comprises, for example, a skin lubricant which reduces a frictional force between the shaving head and the skin surface. The shaving aid may be permanently present in the skin-contacting member or it may be secreted when the skin-contacting member contacts the skin surface. The skin-contacting member may additionally serve as a skin-supporting member, resulting in a reduction of the number of parts used in the shaver.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.